Embodiments of the present invention relate to a method for manufacturing a highly-integrated semiconductor device, and more particularly to a contact that enables the highly-integrated semiconductor device to be stably operated, and a method for manufacturing the contact.
Generally, a semiconductor is a material that has an electrical conductivity that falls in an intermediate region between a conductor and a nonconductor. Although the semiconductor is similar to a nonconductor in a pure state, the conductivity of the semiconductor device may be increased by doping or other manipulation. The semiconductor is used to form a semiconductor device such as a transistor through doping and various deposition and removal processes. An example of the semiconductor device is a semiconductor memory device. The semiconductor memory device includes a variety of constituent elements such as a transistor, a capacitor, etc. Such elements are interconnected through a contact, so that electrical signals can be passed between them. The semiconductor memory device has been rapidly developed to reduce power consumption as well as increase the read/write speed.
As a design rule is reduced to 100 nm or less so as to increase the integration degree of the semiconductor memory device, a cross-sectional area occupied by constituent elements of the semiconductor memory device is reduced, resulting in various problems. For example, a channel length of the transistor is shortened so that a short channel effect such as a punch-through occurs. When forming a contact, an alignment error is increased so that contact resistance is also increased. As spacing between neighboring constituent elements is gradually reduced, it becomes difficult to electrically insulate between the constituent elements. As a result electrical interference caused by parasitic capacitance and the like is increased, so that operation stability and reliability of the semiconductor memory device is reduced.
In recent times, as the integration degree of the semiconductor device is increased, an active region is reduced in size. For example, in a fabrication process of 40 nm or less in an 8F2 structure, a process for forming a device isolation region defining the active region is also becoming difficult. In addition, as the width of a gate pattern is gradually reduced, an aspect ratio of the gate pattern is increased, resulting in a defect such as a leaning of gate pattern. In addition, from the viewpoint of a gate pattern, if the degree of overlap is increased because of an alignment error encountered between a recess region formed when a trench formed in an active region is buried and a pattern formed over the active region occurs, various problems may arise (for example, increase in resistance, reduction in fabrication margin for contact formation, etc.).
As the degree of integration increases, the contact size needs to decrease. If a small-sized contact is formed, resistance is increased, so that an operation for reading and writing data from and in a unit cell may not be smoothly carried out. In order to guarantee a fabrication margin for contact formation, a buried gate structure may be used, but an unexpected problem between a bit line and a storage electrode contact may be encountered.
In the case of a 6F2-structured cell region including a plurality of unit cells in a semiconductor memory device, spacing between neighbor constituent elements is very small and an overlap margin is reduced. This makes it more difficult for a fabrication process for coupling a storage node contact (SNC) and a bit line contact (BLC) to active regions located at both sides of a gate pattern. In addition, if a fabrication error occurs because the spacing between the SNC and the BLC becomes smaller, the possibility for causing an electrical short between the SNC and the BLC is very high. In order to prevent an electrical short between the SNC and the BLC, an insulation film is heavily formed at the sidewalls of the SNC and the BLC, resulting in an increased fabrication margin.
However, assuming that the insulation film is heavily formed at the sidewalls of the SNC and the BLC, there arise a variety of shortcomings. Some example shortcomings are a reduction in an overlap margin that enables the SNC and the BLC to be coupled to the active region and an increased resistance caused by a reduction in overlap degree between the SNC and the active region. In order to increase the size of a contact region, a method for forming a contact by partially etching some parts of the active region may be used. However, the aforementioned method also has a disadvantage in that the depth of a junction part of electric charges is increased when the electric charges are stored in a storage electrode, so that an overlap part between the storage electrode and the channel region is increased. In conclusion, a gate induced drain leakage (GIDL) is increased, and a channel length is reduced, resulting in deterioration of the operation characteristics of the semiconductor device.